The wealth of data of plant researchers

Which plant species grow where, alongside which others - and why? Researchers at the University of Halle and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig have the answer. They have set up the world's first global database on the earth's vegetation. Professor Helge Bruelheide, head of the international project, explains what can be explored with such a wealth of data.

It was none other than Albrecht Dürer who studied a piece of meadow around 1503. The Renaissance artist captured his observations in the watercolour “The Great Piece of Turf”. The artwork depicts various plants and grasses on a swampy subsoil, from the greater plantain to the dandelion and the yarrow. They are portrayed in such detail that the species can be precisely identified. Dürer's painting is therefore described as one of the most famous nature studies in art history. It is also regarded as a forerunner of the vegetation surveys that hundreds of scientists have been producing for about 100 years on every continent of the world. Unlike Dürer, they do more than capture images of the places. They also record where and how many plant species live together. This results in complete lists of plant species from real locations with precise coordinates. Additional information such as soil conditions and the stratification of the vegetation is also noted. The areas in which the plants are identified range from the size of a coaster for small moss grasslands to several thousand square metres for tropical forests.

“We know what's actually there,” says Professor Helge Bruelheide. “Most importantly, we know which species grow where. That means we know the extent of the biodiversity.” The geobotanist is a professor at the University of Halle and co-director of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. He heads the “sPlot” initiative, which has led to the establishment of the first global database on the earth's vegetation at iDiv. In November 2018 it presented its first lists of more than 1.1 million plant species for all mainland ecosystems. And the database continues to grow, currently containing over 1.5 million vegetation surveys - a huge number that is not just a coincidence. Over 170 researchers from all over the world are involved in the project, each adding national or regional databases to “sPlot”. Some of these researchers work at Halle’s Institute of Biology, such as Dr Ute Jandt, who is in charge of the data for Germany, and Dr Francesco Maria Sabatini, who is the project’s overall coordinator. “There are many more people who have worked alongside us,” says Bruelheide. Several dozen scientists have been working for years on a vegetation survey in the tropical rainforest. Working conditions are made more complicated by unpaved roads and wild animals, such as snakes or mosquitoes. Often the plants can barely be distinguished from one another when they do not bear fruit or flowers for most of the year.

Many of the species identified by the researchers and recorded in "sPlot" can also be found in the Botanical Gardens of the University of Halle. “Here you get a good picture of how difficult field work can be under such conditions,” observes Bruelheide standing between palm trees and ferns inside the Great Tropical Greenhouse.

The research group has combined "sPlot" with another iDiv database. The “TRY” database contains over 1,000 characteristics of more than 80,000 plant species. For example, it provides information on how thick the leaves of a plant are, how big it can grow and what its fruit look like. “This has enabled us to find answers to questions that had, until recently, gone unanswered,” says Bruelheide. In one project, for example, the scientists are investigating how similar or dissimilar invasive species are to the species in plant communities into which they spread. “Charles Darwin had already posited the idea that invasive species have an advantage over the native species of a region if they possess different characteristics. For example, the ragweed “Ambrosia artemisiifolia” is native to America. While the pollen of other plants spreads during spring and summer, this type of ragweed flowers from July to October. “This is a particularly significant aspect for human health because the plant can cause severe allergies at a time when the domestic pollen season is actually over,” explains the geobotanist.

In another greenhouse in the Botanical Gardens stands the Chinese windmill palm “Trachycarpus fortune”. “It is also an invasive species in Europe,” explains Helge Bruelheide. “Residents of Ticino have planted them all over their gardens.” It spreads naturally. “This means that palm trees are now growing in the forests of southern Switzerland.” The researchers also regard this as a sign of climate change. “Temperatures have been steadily rising and conditions have become more and more conducive for the palm tree.”

Can "sPlot" also be used to predict further consequences of global climate change? Approximately 10,000 vegetation surveys of sites in Germany have already been repeated in order to detect changes over time. The data are currently being evaluated at the Institute of Biology. In one of the projects, researchers are hoping to draw conclusions about changes in biodiversity at a global level. Helge Bruelheide can already anticipate one result: Over the past 50 years there has been a decline in the diversity of plant species in Germany. Some invasive species are now growing in more and more places. “The winners are always the same, only the losers differ. I find this to be a very threatening trend.” The data collected in “sPlot” provides researchers with information on endangered plant species that have yet to appear in global red lists.

The researchers first want to close the gaps in the database. The next version, which will be published in summer 2019, will also contain vegetation surveys of countries such as Japan and Cuba. “The data has already been collected somewhere in the world,” says Bruelheide. But it is difficult to convince researchers to share the results of their decades of work. “The most fascinating thing about the database is that we've actually managed to get so many people involved in this project.” There are also plans for an open access version of “sPlot”, which will make a large dataset freely accessible - in the interest of all those who want to learn more about the earth’s vegetation.